Radio repeater system



Nov. 23 ,1926. 1,607,683

DE LOSS K. MARTIN RADIO REPEATER SYSTEM F-iled March 22, 1924 El 5 F1215,

UNTED STATES PATENT GFFEQE.

DE LOSS K. MARTIN, 0F V/"EST ORANGE, NEVI JERSEY, ASSIGNOR T0 AMERCAN TELE- PHONE AND TELEGRAPH CQMPANY, A. CGRPORATON UF NEW YORK.

Application filed March 22, 1924.

This invention relates to radio signaling systems, and particularly to a method and means for operating a system employing a single repeater station between the terminal stations thereof, which method is characterized by the changing of the frequencies of the received waves at the repeater station in accordance with a definite pla-n, whereby singing of the repeater or between the repeatervand a terminal station may be prevented and whereby the number of frequencies per channel does not exceed three.

In the operation of a long distance radio system having one or more repeaters between the terminal stations thereof, it has heretofore been necessary to change each received frequency of each transmission channel at each repeater to a different frequency in order to prevent currents transmitted from the same repeater from entering the receiving circuits thereof or the receiving circuits of other channels at a distant repeater or terminal station. For a system without repeaters, two frequencies are normally required for each two-way channel, one for transmitting in one direction and another for transmittingin the opposite direction. Considering, for the purpose of illustration, a system of the prior art having two terminal stations and a single repeater therebetween, if 4we transmit from one terminal a frequency f1 and from the other a frequency f2, singing may be prevented only by changing at the repeater the frequency f, to a third frequency such as f3 before radiating it therefrom to the distant terminal to which it is intended to go; and similarly, by changing the frequency f2 to a fourth frequency such as f4 before radiating it therefrom. wWhile singing will thereby be avoided bot-h at the repeater station and also with the terminal stations, it is obvious that this result is obtained only by a liberal use of the frequency spectrum since the system requires four frequencies to effect two-way transmission between terminal stations of a system involving only one repeater.

It is the object of the present invention to provide a method and means for effecting two-way communication between two radio stations of a system employing a repeater therebetween, the said Vmethod being RADIO REPEATER SYSTEM,

Serial No. 701,187.

quency, translating the received waves into*y waves whose frequencies differ from each other, and transmitting the waves asthus translated.

his invention will be clearly understood from the following description when read in connection with the attached drawing of which Figure l shows in schematic forni an embodiment of the invention; Fig. la shows a mocification of a detail of Fig. l; Fig. 2 shows the reception characteristic of an antenna structure of the form shown in Fig. l, comprising a loop and a vertical antenna; and Figs. 3, 3a, 4tand l show the frequency distribution of a system of communication in which this invention is embodied.

In Fig. l there are represented two terminal stations, designated, respectively, the west station and the east station, and a repeater station intervening therebetween, the function of which is to receive waves transmitted from the terminal stations, to translate and amplify the same and to transmit to the respective terminal stations the waves as thus acted upon. At the west station there is represented a transmitting antenna TA, Vand a receiving antenna BA1, each of which has connected therewith a circuit for transmitting and receiving, respectively. Similarly, at the east station there are provided the transmitting antenna TA2 and the receiving antenna RA2 with suitably associated circuits, which may be of any well-known type. VThe repeater station comprises the receiving antenna structures and RAM the former of which is made up of the vertical antenna l and the loop antenna 2 with the condenser 3 for tuning the same. The antenna structure RA4 comprises similar elements. Connected with the antenna structure RAS is the bandfilter F1, a modulator M1, a second band filter F2 and an amplifier A1, the output side of which is connected with the transmitting antenna TAS. Similarly, the antenna structure Rl'has connected therewith the filter F5, the modulator M2, the filter F6 and the amplifier A the output side of which is connected with the transmitting antenna is a source of high frequency cillations connected with a harmonic producer lill, which, as its title signifies, is adapted lo produce a plurality of harmonics of the fundamental frequency created by 0,. il, and F4 are filters each adapted to pass a certain harmonic produced by H1.

The riceiving antennae RAS and Rif/r4 are designed and adjusted in ways well-known to those sliilled in the art for receiving signals efiicientljv from only one direction. lt is well-known that an antenna structure coni.prising1 a vertical antenna, such as l and :o loop, such as 2, may have al, clniracteristics, such as shown in ants of each antenna circuit and by p1 rer orientation of the loop, the combined structure may be caused to receive most efficiently from one direction only, as shown by the characteristics constituting Fig. 2. For example, the antenna structure RA, may be adjusted to receive efficiently from the west, ria, signals transmitted from the antenna Triand the antenna structure Re may in like manner be adjusted to receive efficiently from the east, that is, the frequency transmitted from the antenna structure TA, of the east terminal station.

The manner in which the aforedescribed system operates is as follows:

Let it be assumed that the transmitting frequency from both terminal stations is f4, as shown in Fig. 3. Oseillations of this frequency from both directions will fall upon the antennae RAS and RA, of the repeater station RR, located therebetween. Assuming' that the antenna RA, has the reception charactertistic represented by the left-hand diagram of Fig. 2, it will receive efficiently the waves of the frequency F4t transmitted from the antenna TA, of the west station and will be substantially unaffected by waves of the same frequency transmitted from the antenna TAZ of the east station. The oscillations of the frequency f4, which, for the jnirpese of illustration may he assumed to he of 750 kilocycles, will be passed by the `filter Fl and be impressed upon the modulator M1. Let it be assumed also that the oscillator O, is generating a wave of kilocycles which is impressed upon the harmonic producer H, adjusted to create therefrom the second and third harmonics, viz, waves of l0() and 150 lrilocycles. lf the filter il, is adjusted to pass a frequency of kilo-- cycles and the filter FQ, `kilo ycles, oscillations of the former frequency will be inipressed upon the modulator M, and will therein beat with the incoming frequency of T50 lrilocycles, producing two frequencies, S50 and 650 kilocycles, that is, the sum and the difference frequencies. If the lter F2 is adjusted to pass only the difference frequency, viz, 650 kilocycles, oscillations of that frequency only will be impressed upon the amplifier A, and, when amplified, will be impressed upon the transmitting` antenna Tfr, and radiated therefrom. @seillutions of this frequency will be impressed upon the receiving` antenna RAZ tuned for the reception of this frequency and will in turn be impressed upon the receiving circuit of the east station. This frequency, which is rcp resented upon Fig. 3 by will not set up interfering oscillations in the receiving antenna RA., or in any of the receiving circuits if the frequency f2 is sufficiently widely separated in the frequency spectrum from the frequency for which each antenna is tuned. In like manner the frequency f4 transmitted by the antenna TA2 of the east station will affect the antenna structure RAM which, as shown in Fig. 2, is intended to receive efficiently from the east, but to be substantially unaffected by waves of the same frequency from the west. rlhe oscillations received by Rete4 will be modulated in the device M2 by the third harmonic produced by the device H1, which will be passed by the filter f, to the modulator M2. Since the third harmonic is 150 lrilocycles and the received oscillations are of the frequency of 750 kilo cycles, the resultant oscillations produced by beating will be 900 and 600 kilocycles. lf the filter FG is adapted to pass the difference frequency, viz, 600 lrilocycles, oscillations of this frequency will be impressed upon the amplifier A2 and, when amplified, will be transmitted by the antenna TA1. These oscillations will, with the arrangement shown in the drawing, be radiated in all directions, but by tuning the receiving` antenna R, of the west station for the reception of this frequency, they will be received only by this station and will produce no interference in other rece' y'ing circuits. It will accordingly be seen that with the arrangement shown in the drawing' and following the method outlined in this specification, two way communication through a system employing two terminal stations and a single rep eater station located therebetween may be accomplished hy the use of three frequencies without creating any interference, that is, singing. of the repeater circuit itself, or between the repeater station and a terminal station.

The other diagrams 3a, 1l and fi represent other modes of distribution of the frequencies throughout the system, but in any case the total number of frequencies involved does not exceed three. ln Fig. 3, the frcquency f, is received from both directions at the repeater station, and transn'lission to the west is accomplished over the frequency /J and to the east by the frequency :u which is opposite to the system of distribution shown in Fig. 3. In Fig. el, the received frequency f, is between the frequencies transmitted from the repeater station, viz, transmission lll to the east is over the frequency f2, which is below the frequency y2, and transmission to the east is over the frequency f3 which is above the received frequency f4. the system of distribution shown in Fig. 4, it is necessary to select the difference frequency resulting from modulation when transmitting to the east and to select the sum frequency resulting from demodulation when transmitting to the west. The arrangement shown in Fig. 4"t is simply the opposite of that shown in Fig. 4.

ln the frequency distribution diagrams, Figs. 3 to 4a inclusive, the frequency difference between f3 and f4 is not equal to the difference between f2 and f4. However, such `inequality is not essential to the operation of the system. By the proper selection of the beat frequencies, these differences may be equalized. For example, in Fig. 4 if f4 represents 750 kilocycles, by using the same harmonic of lrilocycles, as for example, 100 kilocycles and selecting in one case the sum and in the other case the difference frequency of modulation, that is 850 and 650 kilocycles, the difference between f3 and 7L', willequal the difference between f2 and f4. Furthermore, by proper selection of the beat frequency the difference between f2 and f4 may be made equal to that between f2 and Fig. l shows a modification of the Yneans for producing the modulating frequencies at the repeater station. In Fig. 1, there is shown a local source of oscillations O1. In the arrangement shown in Fig. 1a a separate antenna is provided timed for the reception of a fundamental frequency f1, which may be transmitted, for example, from one of the terminal stations. From this fundamental frequency, the requisite harmonics would be produced by thevdevice H1.

lt is desired to clearly set fort-h that while reference has been made throughout the de scription of my invention of the use of a single frequency, as, for example, f, or f3, as representing the transmitted or received frequencies constituting a transmission channel, it is to be understoodv that the designation of these channels by single frequency wares is for the purpose of rendering the description simple and therefore clear, but it is not to be construed as limiting the inven tion in any way to transmission or reception upon a single frequency. The transmitted and the received waves of each channel may, of course, be a side band of frequencies vproduced by the modulation of a carrier frequency by the frequencies within the. voice range, such asis done in radio telephony, or by the modulation of a carrier frequency by telegraph frequencies, such as if; employed in radio telegraphy. lVhile this invention has been disclosed as embodied in a particular form and arrangement of parts, it is not so limited but is To effect capable of embodiment in other` forms with'- out departing from the spirit and scope of the appended claims.`

l/Vhat is claimed is:

.1." ln a radio repeating system-having tern'iinal 'stations and a single repeater station located therebetween in which two-way signaling is effected by using at each termi* nal station a transmitting wave of different frequency from the receiving wave, the method of limiting to three the number of frequencies used throughout the system for each channel of communication which consists in selectively receiving at the repeater station east and west waves of the same fre quency simultaneously, changing the frequency of both of the received waves, and transmitting the waves of changed frequency.

2. In a radio repeating system having terminal stations and a single repeater station located therebetween in which twoway signaling is effected by using at each terminal stationy a transmitting wave of different frequency from the receiving Wave, the method for limiting to three the number of frequencies used throughout the system for each channel of communication which consists in selectively receiving at the repeater station east and weet waves of the same frequency, changing the frequency of one wave by an amount differing from that by which the other wave is changed, and transmitting the waves of changed frequency.

3. In a radio repeating system having terminal stations and a single repeater station located therebetween in which twoway signaling is effected by using at eac'h terminal station a transmitting wave of different frequency from the receiving wave, the method for limiting to three the number of frequencies used throughout the system for each channel of communication which consists in selectively receiving east and west waves of the same frequency, creating a modulating frequency, producing harmonics of the modulating frequency, beating one of the received waves with one of the liar monies, and selecting one of the frequencies resulting from demodulation, beating the other received wave with the other harmonic, and selecting one of the frequencies resulting from demodulation and transmitting both selected frequencies.

4. In a radio repeating system having terminal stations and a single repeater station located therebetween in which two-way signaling` is effected by using at each termiu nal station a transmitting wave of different frequency from the receiving wave, the method for limiting to three the number of frequencies used throughout the system for each channel of communication which consists in selectively receiving east and west waves of the same frequency, beating one of the said waves with oscillations of a fxed frequency, and selecting one of Jche frequencies resulting from the said beating, beating the other of the said Waves With r oscillations of a second fixed frequency which s different from the rst Xed frequeney, selecting one of the frequencies re- DE LOSS K. MARTIN. 

